Microelectromechanical systems (MEMS) include mechanical and electrical components having dimensions on the order of microns or smaller. MEMS structures are used in numerous applications including microsensors and microactuators.
Microsensors can be used to sense and/or measure pressure, flow, acceleration, temperature and stress, amongst other conditions. A microsensor functions by generating electrical signals in response to movements of a mechanical component of the sensor. The sensor may be calibrated such that the electrical signal and, thus the movement of the mechanical component, is correlated to the condition.
Microactuators include one or more mechanical components (e.g., valves, beams, diaphragms, and mirrors) which are moved to perform a desired function. Complex microactuators structures may include multiple movable mechanical components, for example, to form a micromotor. A microactuator functions in a manner opposite, in some regard, to that of a microsensor by converting an electrical signal to a mechanical movement.
MEMS structures may be formed using microelectronic fabrication processes. In a typical process, deposition steps are used to deposit layers which are subsequently patterned using lithographic and etching steps to form the desired mechanical and electrical components. Other conventional processing steps, such as ion implantation, may also be employed if necessary.
Because microelectronic fabrication processes can be used to form MEMS structures, mechanical and electrical components of the structures are oftentimes formed of silicon. However, one disadvantage of silicon-based MEMS structures is the loss of performance under extreme conditions such as high temperatures, corrosive environments, or rapid vibrations. Under such conditions, the mechanical properties of silicon may be degraded so that the mechanical components cannot perform their desired function. Also, silicon becomes extrinsic at temperatures above 150° C. and, thus, loses its ability to function as a semiconductor material at such temperatures.